1. FIELD OF THE INVENTION
This invention relates to a process for the recovery of a heavy metal from an aqueous solution containing the heavy metal.
The recovery of heavy metals from various aqueous solution containing a small amount of the heavy metals such as seawater, water of river, lake, or swamp, or waste water drained from industrial processing apparatus is advantageous not only for removing unfavorable heavy metals but also for collecting valuable heavy metals.
Particularly, seawater contains approx. 3 .mu.g/1. of uranium dissolved therein. Since uranium is of great value as fuel for nuclear reactor, a process for efficiently recovering uranium from seawater which contains totally a great amount of uranium is earnestly desired.
2. DESCRIPTION OF PRIOR ARTS
There have been known arts for recovering uranium from seawater or the like containing a small amount of uranium which employ various adsorbents. Examples of the adsorbents include inorganic adsorbents such as titanic acid, gelana, and active carbon-titanic acid adsorbents, and organic adsorbents such as resinous adsorbents, for instance, resorcinol-arsonic acid-formaldehyde resin, and amidoxime-containing resin. Among these adsorbents, the organic adsorbents are considered to be preferably employable in industry because the organic adsorbents are easily moldable and readily handled. Nevertheless, known adsorbents for the recovery of uranium have certain drawbacks such as poor adsorbing efficiency, poor strength for the employment as the practically usable adsorbents. Accordingly, improvements in the adsorbents have been desired.
At present, it is known that a polymer containing acid hydrazide groups can adsorb heavy metals such as mercury, copper, nickel, silver, zinc, cobalt, and the like contained in an aqueous solution. However, this acid hydrazide group-containing polymer shows very poor adsorbing efficiency for uranium dissolved in an aqueous solution such as seawater. Thus, this polymer is not advantageous in practical use as the absorbent for uranium. Further, the use of a polymer prepared by reaction of the acid hydrazide group-containing polymer with pyridinealdehyde is proposed. However, the adsorbing efficiency of this polymer is still too low to employ as the adsorbent in industry.